Berezinskii-Kosterlitz-Thouless phases in ultrathin PbTiO3/SrTiO3 superlattices

Fernando Gómez-Ortiz, Pablo García-Fernández, Juan M. López, and Javier Junquera
Phys. Rev. B 106, 134106 – Published 17 October 2022

Abstract

We study the emergence of Berezinskii-Kosterlitz-Thouless (BKT) phases in (PbTiO3)3/(SrTiO3)3 superlattices by means of second-principles simulations. Between a tensile epitaxial strain of ε=0.251%, the local dipole moments within the superlattices are confined to the film-plane, and thus the polarization can be effectively considered as two-dimensional. The analysis of the decay of the dipole-dipole correlation with the distance, together with the study of the density of defects and its distribution as a function of temperature, supports the existence of a BKT phase in a range of temperature mediating the ordered ferroelectric (stable at low T), and the disordered paraelectric phase that appears beyond a critical temperature TBKT. This BKT phase is characterized by quasi-long-range order (whose signature is a power-law decay of the correlations with the distance), and the emergence of tightly bound vortex-antivortex pairs whose density is determined by a thermal activation process. The proposed PbTiO3/SrTiO3 superlattice model and the imposed mechanical boundary conditions are both experimentally feasible, making it susceptible for an experimental observation of these new topological phases in ferroelectric materials.

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  • Received 20 July 2022
  • Revised 8 September 2022
  • Accepted 5 October 2022

DOI:https://doi.org/10.1103/PhysRevB.106.134106

©2022 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Fernando Gómez-Ortiz1, Pablo García-Fernández1, Juan M. López2, and Javier Junquera1,*

  • 1Departamento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Cantabria Campus Internacional, Avenida de los Castros s/n, 39005 Santander, Spain
  • 2Instituto de Física de Cantabria (IFCA), CSIC–Universidad de Cantabria, 39005 Santander, Spain

  • *Corresponding author: javier.junquera@unican.es

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Issue

Vol. 106, Iss. 13 — 1 October 2022

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